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Homework Help: Calculate the distance from the center of the Earth

  1. Nov 14, 2004 #1
    Calculate the distance from the center of the Earth to a point below the surface where the acceleration due to gravity is 0.50g, where g is the acceleration due to gravity at the Earth's surface.
    I thougtt I could use g = GMe / R^2 solving for R. But this did not work.
    This problem seems really simple I just cant seem to figure it out.
  2. jcsd
  3. Nov 14, 2004 #2

    Doc Al

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    Staff: Mentor

    That equation is only good for points at or above the earth's surface. You need to figure out the force of gravity beneath the surface, for r < Re. Hint: treat the earth as a sphere of uniform density. The gravity experienced at any given distance from the center r depends only on the mass located beneath that point (the force from the shell of mass above the point cancels out).
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